1. Field of the Invention
The present invention relates to a light-emitting device and the like that causes a light-emitting layer to emit light in accordance with an applied voltage provided between a pair of electrodes.
2. Description of the Related Art
In recent years, there has been a tremendous amount of development in the type of flat panel display called the organic electroluminescent (hereinafter abbreviated “EL”) display, which utilizes organic EL phenomena to display images.
The organic EL display is a self-luminous light-emitting display that utilizes the luminous phenomena of the organic electroluminescent device to display images, making it possible to achieve a thin display that is light in weight and offers a wide viewing angle and low power consumption. The organic electroluminescent device forms an organic semiconductor layer between two electrodes, and a light-emitting layer on a part of this organic semiconductor layer (refer to JP, A, 2007-12369).
In the organic EL display of prior art, the light generated by the light-emitting layer inside each organic electroluminescent device is guided in the substrate and the organic semiconductor layer in the direction (horizontal direction) in which that layer extends, at a percentage of approximately 80%. As a result, the organic electroluminescent device of prior art has a light extraction efficiency in the frontal direction of the organic display of only approximately 20% in general, resulting in poor light extraction efficiency and difficulties in increasing luminance.
In consequence, there have been known prior art organic electroluminescent devices that provide within the organic semiconductor layer a functional layer (hereinafter “light extraction improving layer”) designed to improve the light extraction efficiency from the light-emitting layer [refer to JP, A, 2008-28371 and JP, A, 2008-59905]. Such prior art discloses a configuration in which a light extraction improving layer that contains at least Ag in part as a component is formed adjacent to a transparent electrode.
While the prior art described in the above JP, A, 2008-28371 and JP, A, 2008-59905 discloses a configuration wherein a light extraction improving layer containing at least Ag in part as a component is formed adjacent to a transparent electrode, the value of the refractive index n of the transparent electrode in this case is approximate 2.0 or higher which is large, thereby minimizing any gain in emission intensity since light, by its very nature, is guided in the direction of the higher refractive index n. In particular, with the large difference between the refractive indices of the transparent electrode and the Ag layer, the above guidance characteristics occur to a significant degree.